1. Technical Field
The present disclosure is directed to a camera sensor module, and more particularly to an array of high-resolution infrared pixels having a reduced pitch between the pixels.
2. Description of the Related Art
Current infrared sensors are widely used in a variety of commercial and governmental applications. For example, infrared sensors detect a presence of a person in a room by detecting temperature changes, such as when a person enters a room. This is a relatively simple detection that can be achieved with a couple of pixels that have a 300 micrometer pixel pitch. Other infrared sensors detect body temperature measurements and can be used for thermal imaging, such as thermography. Body temperature measurements can be achieved with low resolution sensors, e.g., a 200 pixel sensor with 100 micrometer pixel pitch.
There are many commercial applications of infrared sensors, such as technicians identifying overheating joints or sections of power lines, which can be a sign of impending failure of the line. These sensors can help identify heat leaks in thermal insulation, which can result in making buildings and homes more energy efficient.
Infrared sensors detect radiation in the infrared range of the electromagnetic spectrum, which ranges from 750 nanometers to 1.0 millimeters (0.75 to 1000 micrometers). All objects emit infrared radiation, which means that images of an environment can be created with or without illumination from the visible range. The amount of radiation emitted by an object increases with temperature, which allows an infrared sensor to detect subtle variations in temperature.
Thermal imaging cameras provide images where warmer objects stand out against cooler backgrounds and background objects. For example, living beings are easily visible with an infrared sensor even without light from the visible spectrum. Higher resolution infrared sensors, like these, are useful in automotive safety, such as providing video imaging showing living beings during the night or other low light conditions. These are medium resolution sensors having approximately 2000 pixels with 25 micrometer pixel pitch.
Bolometers are infrared sensors that detect incident electromagnetic radiation by heating a material that has a temperature dependent electrical resistance. An increase in temperature is used to measure a radiant energy. Microbolometers, such as the microbolometer 100 in FIG. 1, are bolometers that can be used as a detector in a thermal camera to detect infrared radiation. The microbolometer 100 includes an infrared absorbing material 102 suspended above a substrate 106. When a photon strikes the absorbing material 102, the photon passes through the absorbing material 102 hits a reflector 104 and bounces back up through the absorbing material 102. The absorbing material increases in temperature as the number of photons passing through the absorbing material increases. The change in temperature provides the data read out by circuitry in the substrate.